The present invention relates to an oil pan of an engine mounted on a vehicle. More particularly, the present invention pertains to an oil pan that has a sub-oil chamber to increases the volume of an oil reservoir and to an apparatus for forming such oil pans.
A typical vehicle engine includes an oil pan fixed to the lower part of the cylinder block. The oil pan has a reservoir for storing oil, which is supplied to the moving parts of the engine. The reservoir must be large enough to store the oil required by the moving parts of the engine. However, the size and shape of the space allocated for the engine in the engine compartment limits the vertical dimension of the oil pan, which may restrict the volume of the oil pan. If the oil pan is formed by deep-drawing sheet metal, the vertical dimension of the oil pan is limited by the deep-drawing process. Therefore, even if an adequate space exits in the engine compartment, the oil pan cannot be made deep enough. As a result, the volume of the reservoir is not sufficient.
Insufficient reservoir volume causes the oil to deteriorate in a relatively short time. Therefore, the moving parts of the engine are not sufficiently lubricated. Insufficient lubrication wears the moving parts, which increases engine vibration and noise and lowers the fuel economy. The oil, therefore, must be frequently changed.
If the volume of the reservoir is too small yet the reservoir stores a sufficient amount of oil for the engine to function normally, the level of the oil becomes relatively high. The oil in the reservoir is vibrated by the engine, which causes the oil to interfere with moving members such as the connecting rods and the crankshaft. This increases rotational resistance, creates bubbles in the oil, increases the oil temperature and degrades the oil.
To solve this above problem, oil pans having baffles have been introduced. A baffle is fixed to the inner wall of the reservoir and extends over the surface of the oil such that oil contacts the baffle when vibrated. The baffle needs to be fixed to the inner wall by welding, which complicates the manufacture of the oil pan. Further, the joint between the baffle and the oil pan may deteriorate or fail due to engine vibration and to the force of the vibrating oil.
FIG. 15 shows a prior art oil pan 100. The oil pan 100 has sub tanks 101 to increase its volume. The sub tanks 101 are separately formed and welded to the side walls 102 of the oil pan 100. A side chamber 101a, which is defined in each sub tank 101, is connected to the reservoir 100a of the oil pan 100. However, since the sub tanks 101 are formed separately from the oil pan 100 and the sub tanks 101 are welded to the oil pan 100, the manufacturing process is troublesome. Further, the joints between the sub tanks 101 and the oil pan 100 are easily damaged and deteriorate quickly.
Accordingly, it is an objective of the present invention to provide a durable oil pan that stores a relatively large amount of oil and is easy to manufacture.
Another objective of the present invention is to provide an apparatus that easily forms the above oil pan.
To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, an oil pan having surrounding wall defining an oil reservoir and a horizontally projecting bulge formed in the surrounding wall is provided. The bulge is integrally formed with the surrounding wall by outward deformation. The bulge defines an oil sub chamber connected to the oil reservoir.
The bulge is formed integrally with the surrounding wall of the oil pan. Unlike the prior art oil pan, the bulge does not have to be welded to the surrounding wall but is easily and inexpensively formed by pressing. Further, there is no joint between the surrounding wall and the bulge, which improves the strength and durability. The bulge also improves the rigidity of the surrounding wall.
The bulge preferably has an upper wall, which faces the surface of the oil. The upper wall is located above the surface of the oil in the reservoir.
When the engine is running, the surface of the oil in the reservoir is vibrated. However, the vibration is received by the upper wall of the bulge, which suppresses the vibration. This structure eliminates the necessity for a baffle attached to the inner wall of the oil pan for suppressing oil vibration. Therefore, problems caused by baffle plate, specifically, a complicated manufacturing process and deterioration of the joint, are avoided.
The present invention includes an apparatus for forming the above described oil pan. The apparatus includes a base, a first stage, a fixed hollow die, a tool, an outer die, a second stage, a first cam mechanism and a second cam mechanism. The first stage is moved closer to and away from the base. The fixed hollow die is located on the first stage. The outer shape of the fixed die corresponds to the inner shape of the oil reservoir. The fixed die includes an opening, the shape of which corresponds to the bulge. The tool is located in the interior of the fixed die to be movable in a direction substantially perpendicular to the moving direction of the first stage. The tool includes a projecting die, which can protrude from the opening of the fixed die. The outer shape of the projecting die corresponds to the inner shape of the bulge. The outer die is located on the first stage and is being movable in a direction substantially perpendicular to the moving direction of the first stage. The outer die moves toward and away from the fixed die. The outer die includes a recess, the inner shape of which corresponds to the outer shape of the bulge. The second stage faces the first stage with the outer die in between and is movable in the same direction as the first stage. The first cam mechanism is located between the base and the tool. When the first stage is moved toward the base, the first cam mechanism moves the tool such that the projecting die protrudes from the opening of the fixed die. The second cam mechanism is located between the second stage and the outer die. When the second stage is moved toward the first stage, the second cam mechanism moves the outer die toward the fixed die.
This apparatus facilitates the manufacture of oil pans having an integrated bulge. Particularly, the first and second cam mechanism causes the bulge to be formed simply by moving the first and second stage in one direction.
The present invention also includes a method of forming an oil pan. The method includes: placing a partially formed oil pan on a forming apparatus, the partially formed oil pan including a reservoir surrounded by a wall and an opening, wherein the opening defines a horizontal plane; and forming a bulge in the wall such that the bulge extends outward from the wall in a direction generally parallel to the horizontal plane, wherein the bulge increases the capacity of the reservoir.
Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.